5.56 vs 300BLK Mags- What Works Best For You?

Get Off My Lawn

Artist formerly known as Pink Vapor
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I'm a looking for deals on a few 30 round mags for my 300BLK rifles, I primarily shoot sonic. All my 5.56 are metal.
Lancer smoke look like an obvious choice for different look and feel. PA's website says, "NOTE: These magazines are optimized for subsonic 300BLK ammunition which have a wider and more forward-oriented ogive on the projectile. If you are shooting lightweight supersonic 300BLK ammunition (<150gr), we recommend using a standard .223/5.56 magazine, as the geometry of most supersonic cartridges more closely mimics that of a .223/5.56 cartridge."
PA has Magpul 300 round 300BLK mags for $11 right now.
https://gunmagwarehouse.com/lancer-...ound-advanced-warfighter-magazine.html#92=182

What say ye, and where's today's best deal?
 
I mainly run PMags for mine. Black for 5.56 and FDE for 300BLK. The stocks/grips/sights (and even the barrel on my 300BLK SBR) follow the same color-coding scheme.

I have some black metal (I think they’re D&H, but I rarely pull them out), and maybe some FDE metal ones.
 
Lancer smoke look like an obvious choice for different look and feel.
This is exactly what I do. Smoke Lancers for 300BLK only. They’re the .223 version, but I will never load .223 in them or .300BLK in Pmags. The risk isn’t worth it.

I had M3 300BLK Pmags, I labeled them differently but if I was moving quickly, I knew I could still confuse them. The Lancers are said to work for 300BLK better than Pmags, even the .223 Lancers. I haven’t tried the .300BLK Lancers (FDE floorplate).

Getting Lancers for $15-16/ea shipped is pretty good. They’re tough to find sales on.
 
I use hexmags for 300BLK, and don't use hexmags for anything else. Makes it easy to not confuse.

I got a little creative coloring along the hex pattern with a silver sharpie and writing "3 0 0" in the little hexes; my friends say it looks too "arts and crafts". Whatever, no one would mix them up and if they're my friends they've already proven themselves to have questionable judgement so who's to say if it's overly artsy or just prudent safety markings?

I've only fired heavy subsonics and 146gr supers out of the 556 mags in the AR but no issues so far. For my Ruger bolt gun I've been using the same magpul pmag10 that came with it to fire every 300BLK round so far and it's a 556 labeled mag with a 556 labeled follower. 491 rounds per the spreadsheet. But it's a bolt gun so it's probably less sensitive to feeding.

All that said, I wouldn't mind a few 300BLK labeled mags even if they're not all that different than 556 just because I like things to match up.
 
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I use hexmags for 300BLK, and don't use hexmags for anything else. Makes it easy to not confuse.

I got a little creative coloring along the hex pattern with a silver sharpie and writing "3 0 0" in the little hexes; my friends say it looks too "arts and crafts". Whatever, no one would mix them up and if they're my friends they've already proven themselves to have questionable judgement so who's to say if it's overly artsy or just prudent safety markings?

I've only fired heavy subsonics and 146gr supers out of the 556 mags in the AR but no issues so far. For my Ruger bolt gun I've been using the same magpul pmag10 that came with it to fire every 300BLK round so far and it's a 556 labeled mag with a 556 labeled follower. 491 rounds per the spreadsheet. But it's a bolt gun so it's probably less sensitive to feeding.

All that said, I wouldn't mind a few 300BLK labeled mags even if they're not all that different than 556 just because I like things to match up.
I read some poor reviews on the Hexmags, I hoped they'd have been a good choice by looking and feeling completely different. How long have you been using them?
 
.300BLK in 20rd black Lancers, 5.56 in 30rd 'GI' mags.

Should probably label the 6.8 mags, though. My PRIs are distinctive enough, but the ASCs & Stoners look just like 20rd 'GI' mags.
 
.300BLK in 20rd black Lancers, 5.56 in 30rd 'GI' mags.

Should probably label the 6.8 mags, though. My PRIs are distinctive enough, but the ASCs & Stoners look just like 20rd 'GI' mags.
FWIW...

I mentioned earlier that all my 5.56 use black, and 300BLK use FDE. Well, my 6.8 gets ODG. Since I can’t buy PMags in 6.8 ODG, I stenciled my D&H/PSA mags with caliber and a stripe that matches the furniture and cerakoted barrel:

D3191028-BEDB-4C5F-8504-EE09E0B187F8.jpeg

They’re really the only non-PMags I use, but the stencil takes it one step further.

30F3BE32-B0C7-41DF-AB6C-1FE53E5C40EF.jpeg

5666D004-AC39-436A-86DD-EEBFA7DBF44B.jpeg

And I don’t have a real good pic of it once I cut the barrel down to ~12” that shows the color, but the it’s definitely ODG. :D

26627FCC-4B45-4757-B7E8-74D8C73442C3.jpeg
 
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I read some poor reviews on the Hexmags, I hoped they'd have been a good choice by looking and feeling completely different. How long have you been using them?

Honestly not that long, or more specifically that many rounds. My 300BLK AR is a range toy, not a fighting rifle so it's not seen much abuse, dirt, heat, etc so the "it always works!" tag doesn't have much meat behind it. My favorite PSA gun, that's been run hard, broken, fixed and run hard again and it's damn reliable... with pmags in 556. So again, zero help to you in this case. Man, I'm just a bundle of useless data tonight.
 
You have to sand down the side ribs at the front of the pmags then they work great. Metal .223 doesn't feed well in my experience as you have those ribs that push he rounds funny.
 
I'm also using electrical tape for 300BLK on the magazines and the mag wells. It's worked just fine for me so far, but I can see how there's a possibility of an issue on a cold, dark night while wearing gloves... I'm not shooting much in those conditions, so that risk seems fairly remote.
 
I only have one dedicate "300" magazine right now.
I printed out the "300" from the "THE 300" logo, made a stencil with some card stock, then dipped a q-tip into the red testors paint I was using for some roll mark color fill, and slapped it on a pmag one boozy night.
it looks kind of neat. The mag worked with subs and supers the couple times I used it...
 
I only have one dedicate "300" magazine right now.
I printed out the "300" from the "THE 300" logo, made a stencil with some card stock, then dipped a q-tip into the red testors paint I was using for some roll mark color fill, and slapped it on a pmag one boozy night.
it looks kind of neat. The mag worked with subs and supers the couple times I used it...

You see how some of the guys upstream posted pictures? Take a swig and post one up.
 
Pee Mags. I run FDE for .300 as well, mainly because it matches the furniture (all by design). I run a 20 round Colt 'ban' mag with the "not for use by ordinary citizens" crap stamped on it while I'm hunting with my AR, just to remind me of the bad times.
 
You see how some of the guys upstream posted pictures? Take a swig and post one up.
sigh. I'm generally quite lazy about that sort of thing, but i'm in a good mood for having drank night 4 of my beer advent calendar and putting together a coarse particle board bench/shelf/storage unit without it completely disintegrating...300.jpg
It started off as a slightly used free float quad rail 10.5" hardened arms upper (my lawyer decided it wasn't right for him) that went on a psa sbr. then somehow I also ended up with my lawyers todd jarrett YHM rail, so that went on instead. And then I suddenly needed a host for a decent upper because i wanted to keep that psa sbr as 5.56, so I slapped together a poverty pony lower. And then somebody sold me that romeo5 for like $50, but i had to pick up a cheap riser from a gun show...
it is ugly. I do not pretend it's pretty. I have some very pretty rifles that live in my safe - this isn't one of them.
but with that pressure pad tied to the AFG, it throws a laser in case I don't want to look in the romeo.
Oh, and that's a gemtech hvt-thd I picked up a while back.
At some point, in one of its rebuild stages, i handed it to my wife's friend who had never fired an AR before. at 50 yards offhand she was grouping a couple inches. She wanted to know how much it would cost to get herself something like it, and I had to explain that you NEVER ask that sort of question in front of a man's wife.
 
sigh. I'm generally quite lazy about that sort of thing, but i'm in a good mood for having drank night 4 of my beer advent calendar and putting together a coarse particle board bench/shelf/storage unit without it completely disintegrating...View attachment 172404
It started off as a slightly used free float quad rail 10.5" hardened arms upper (my lawyer decided it wasn't right for him) that went on a psa sbr. then somehow I also ended up with my lawyers todd jarrett YHM rail, so that went on instead. And then I suddenly needed a host for a decent upper because i wanted to keep that psa sbr as 5.56, so I slapped together a poverty pony lower. And then somebody sold me that romeo5 for like $50, but i had to pick up a cheap riser from a gun show...
it is ugly. I do not pretend it's pretty. I have some very pretty rifles that live in my safe - this isn't one of them.
but with that pressure pad tied to the AFG, it throws a laser in case I don't want to look in the romeo.
Oh, and that's a gemtech hvt-thd I picked up a while back.
At some point, in one of its rebuild stages, i handed it to my wife's friend who had never fired an AR before. at 50 yards offhand she was grouping a couple inches. She wanted to know how much it would cost to get herself something like it, and I had to explain that you NEVER ask that sort of question in front of a man's wife.
Me likes it
Is that Rick Flair’s?
Woo!!

the 3 looks like a W
 
I have 3 .300BLK ARs. Two rifles, one pistol. All three are krylon'd camo. The PMAGS for .300 BLK are krylon'd to match. All my 5.56 rifles and pistols are black as are their mags.

I do have several of the 30 round dedicated PMAGS made for .300 BLK. I've not experienced a failure in any of my standard 5.56 mags running them with .300BLK.
 
I ordered a couple Magpul 30 rnd 300BLK mags from PrimaryArms for $11 each.
From what I've read it only makes a difference with the larger subsonics due to their steeper ogive. The bullets are pushed towards the center instead of forward potentially causing binding/FTF.
 
I ordered a couple Magpul 30 rnd 300BLK mags from PrimaryArms for $11 each.
From what I've read it only makes a difference with the larger subsonics due to their steeper ogive. The bullets are pushed towards the center instead of forward potentially causing binding/FTF.

That explains why I've not had any failures in the standard 5.56 Pmags. I primarily run Supers. I bet I've shot less than two boxes of subs total.
 
That explains why I've not had any failures in the standard 5.56 Pmags. I primarily run Supers. I bet I've shot less than two boxes of subs total.
And most of my subs have been the 187gr Gemtech. No issues so far.
 
I use USGI metal mags with magpul followers for 556 and 300BLK subs and supers. The 300BLK mags get labeled with a paint pen. Been using them for years with no issues yet.
 
You have to sand down the side ribs at the front of the pmags then they work great. Metal .223 doesn't feed well in my experience as you have those ribs that push he rounds funny.
Can you expound on that a bit?

I took out my new 300BLK pistol today. Never had an issue with various ammo weights (subs & supers) in my 10” SBR. But had multiple different ammo variants today eject but not load the next round, both unsuppressed and suppressed. PMags in the SBR and pistol.

Obviously could be several things, but I didn’t bother trying to narrow it down due to other things I wanted to shoot. It did look like with the 220gr the tips were awfully close to the center rib inside the mag. Which made me think of a couple comments in this thread...including yours and the one about the subs pushing toward the center.

Wondering exactly what you’re sanding down, or if trimming a little of the top of the center rib might help.
 
Can you expound on that a bit?

I took out my new 300BLK pistol today. Never had an issue with various ammo weights (subs & supers) in my 10” SBR. But had multiple different ammo variants today eject but not load the next round, both unsuppressed and suppressed. PMags in the SBR and pistol.

Obviously could be several things, but I didn’t bother trying to narrow it down due to other things I wanted to shoot. It did look like with the 220gr the tips were awfully close to the center rib inside the mag. Which made me think of a couple comments in this thread...including yours and the one about the subs pushing toward the center.

Wondering exactly what you’re sanding down, or if trimming a little of the top of the center rib might help.
I finally found a picture! See the 5.56 ribs are pushing the larger sub bullets towards the center.
upload_2019-12-6_18-39-48.png
https://www.shootingillustrated.com/articles/2017/9/24/reloading-300-blackout-must-have-materials/
 
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This is exactly what I do. Smoke Lancers for 300BLK only. They’re the .223 version, but I will never load .223 in them or .300BLK in Pmags. The risk isn’t worth it.

I had M3 300BLK Pmags, I labeled them differently but if I was moving quickly, I knew I could still confuse them. The Lancers are said to work for 300BLK better than Pmags, even the .223 Lancers. I haven’t tried the .300BLK Lancers (FDE floorplate).

Getting Lancers for $15-16/ea shipped is pretty good. They’re tough to find sales on.

Any issues with subsonic through the 223 lancer?
 
Any issues with subsonic through the 223 lancer?
I can’t recall if I’ve shot more than a mag of subs since moving to the Lancers earlier this year. I tested subs a bit, mainly to test the gas system, when I used Pmags, but I generally shoot 125gr supers.
 
I gave my son a 300 BLK upper and a complete 5.56 SBR ( He's on the trust ) and a crapload of ammo for both . I also gave him mags clearly marked for both.

You can guess what happened. Yep. He blew the 5.56 upper up in about 3 months. Destroyed the upper receiver and BCG.
 
I also use Lancer Smoke mags for .300 and Pmags for 5.56. The elanders that I use for 6.5 Grendel are unique enough that I wouldn’t ever worry about putting the round ammo in them.
 
I gave my son a 300 BLK upper and a complete 5.56 SBR ( He's on the trust ) and a crapload of ammo for both . I also gave him mags clearly marked for both.

You can guess what happened. Yep. He blew the 5.56 upper up in about 3 months. Destroyed the upper receiver and BCG.
Sorry to hear that, I imagine he's OK?
What is the plan going forward to try to eliminate future confusion?
 
Sorry to hear that, I imagine he's OK?
What is the plan going forward to try to eliminate future confusion?
Just scared the crap out of him . He gave me the gun back. Lower was ok and so was the barrel believe it or not. We will try again some other time. Problem was he let a friend load the mags.
 
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Just scared the crap out of him . He gave me the gun back. Lower was ok and so was the barrel believe it or not. We will try again some other time. Problem was he let a friend load the mags.
Good point that friends not so familiar with the different calibers/types of ammo could easily make that mistake.

PM sent on deals for parts to fix your upper as to not sidetrack this thread too much.
 
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